Type of modified carbon black Ⅰ
Carbon black is widely used in the rubber suction cup industry, mainly for reinforcing, coloring, conducting, and improving weather resistance. Since the carbon black production process is carried out at a temperature of 140 to 180 ° C, the carbon, hydrogen, sulfur and ash contained in the raw materials react with oxygen in the surrounding air to produce a large amount on the surface of the carbon black. Contains oxygen functional groups.
These functional groups provide surface activity for carbon black and also become a reaction point for chemical modification of carbon black.
Why do you want to modify carbon black? The answer is simple, because carbon black is a high surface energy substance, it is hydrophilic, and rubber is a hydrophobic substance, so the affinity between the two is poor, and the carbon black particles tend to self-polymerize after entering the rubber. , causing agglomeration, affecting its dispersion in the rubber, and thus unable to fully exert the reinforcing function. Therefore, it is urgent to modify the surface of carbon black. This modification is usually achieved by surface coating, surface adsorption, surface grafting, oxidation, halogenation, and the like. Several modifications are briefly described below.
(1) Coating modification
It is an effective way to mix white carbon black with carbon black and modify the latter. The modified carbon black can make the tire have lower rolling resistance at higher temperatures and higher rolling resistance at lower temperatures, that is, better ground grip and anti-slip effect. The resulting carbon black is fully suitable for the practical use of “green tires”. The key is to coat the surface of the carbon black with a suitable coupling agent, such as silane Si69. Specifically, carbon black is mixed with water-dispersed silica to prepare a slurry, and then a modified material containing silane and a dispersant is added. The silica is coated on the surface of the carbon black. This modified carbon black has been used in “green tires”, which are characterized by energy-saving and environmentally friendly tread rubber.
(2) Adsorption modification
Adsorbing the wetting agent or surfactant on the surface of the carbon black to prevent the re-agglomerated carbon black from re-agglomeration, thereby obtaining a stable dispersion system; or using the strong adsorption effect caused by the difference in charge and polarity of carbon black and rubber Excellent dispersion stability is obtained to prevent it from agglomerating again. An effective wetting agent is cetyltrimethylmaleamide
Carbon black structure
The structure is one of the basic properties of carbon black, and the other two properties are particle size and surface properties. It refers to the aggregation state and degree of carbon black elementary particles, and is also a general term for primary structure and secondary structure. Most of the carbon black varieties have a particle size within the nanometer size range (<100 nm), and their surfaces are rich in active groups. Therefore, there is inevitably more or less tendency of aggregation between particles, which is the origin of the structural concept.
The carbon black manufacturing process is always under high temperature conditions, and adjacent particles are simultaneously formed, mutually melted into a chain, and occupy a space of three degrees, which is called a primary structure. In the post-processing stage, a relatively loose structure is formed between the structures due to physical adsorption or van der Waals force or static electricity, which is called a secondary structure.
The fastness of the primary structure is strong and it is not easy to be damaged in the processing of the rubber stopper. This property has a great influence on the vulcanized rubber.
Relatively speaking, the secondary structure is susceptible to damage by mechanical forces during processing, so it is also called a temporary structure.
The influence of the carbon black structure on the performance of the rubber plugs can be divided into two aspects: Firstly, in terms of the physical properties of the vulcanizate, the high carbon black has a good effect on hardness, tensile stress and electrical conductivity. Secondly, the structure also plays a key role in the rubber processing performance. The higher the structure, the more difficult it is to disperse in the rubber and the greater the heat generation.
The height of the carbon black structure can be measured by the oil absorption value, which is the adsorption volume (mL/g) of the oil per unit mass (usually dibutyl phthalate, DBP) per unit mass. According to the level of the oil absorption, the structure of the carbon black can be determined.
In order to obtain the carbon black of the desired structure, it can be regulated in the carbon black manufacturing process. To improve the structure, a feedstock oil with a high aromatic content can be used; to reduce the structure, a metal salt can be added to the feedstock oil and a smaller burner spray angle can be used.
Mold structural elements of rubber grommets
The structural elements of the so-called rubber grommet molds are the various components that make up the rubber mold and the structural forms that perform certain process functions. For the rubber grommet molds that are usually used, the structural elements can be classified into the following eight types.
1 molding elements
Molding elements include upper and lower mold bodies (or stencils), middle mold bodies (plates), end molds, cores, mandrels, cores, cavity inserts, blocks, and other components that make up the mold cavity.
2 auxiliary elements
The auxiliary elements of the rubber grommet mold include the residual glue tank, the running glue tank (or called the glue tank or the overflow tank), the vent hole, the venting groove (ie, the exhaust groove), and the cutting without the flashing rubber mold. Edge cutting edge, rubber sealing groove, etc.
3 connecting elements
Connection elements include screws, nuts, washers, washers, rivets, locking screws, threaded holes, threaded through holes, fisheye holes, countersunk screw holes, special special hinges (including mobile hinges).
4 positioning elements
The elements include a locating pin, a pin sleeve, a locating hole, a taper pin, a tapered pin bushing, a stencil taper pin hole, a guide surface, a guide groove, a guide hole, a HALF block, and the like.
5 glue injection elements
The injection molding elements include a pressure injector (hopper, plunger), an injection port, a main flow channel of the flow channel system, a volume (also referred to as a cold hole), a bypass, a feed port, and the like.
6 process elements
Process elements include process positioning holes, process thread holes, process connection holes, process pin holes, process blockers, and more. The process elements are only for the convenience of the manufacturing and processing of the mold parts, and have nothing to do with the operation of the mold.
7 operating elements
This element includes the handle, the opening (also known as the screwdriver opening, the opening groove), the sleeve, the die hole, the temperature measuring hole, the general or special unloading frame.
Forward From: https://rubber-grommet.com/mold-structural-elements-of-rubber-grommets/
What is a hinged mold?
The hinged mold is a small-sized mold that is operated by manual movement which is usually used, and a special hinge is added to the side surface as a connecting member of the upper and lower stencils. This type of mold is called a hinged mold, see the figure below.
The feature of the hinged mold is to replace the handle on the side of the original mold with a special hinge. In the use of the mold, the mold is opened and closed like a book, which is very convenient to use and does not cause flipping and flipping. phenomenon.
The hinged mold is positioned with a tapered pin or a tapered surface for the structure, and it is not necessary to use various special tools such as a boring bar or a copper screwdriver when starting the mold. Some hinged molds are more convenient when removing products.
Type of modified carbon black Ⅱ
2019年4月21日
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(3) Surface modification of carbon black
The carboxyl group and the hydroxyl group on the surface of the carbon black are reacted with a low molecular compound to form an active point,
Further, graft polymerization is initiated to obtain a modified product having a high graft ratio. The carbon black particles are prevented from re-aggregating under the effect of their steric hindrance.
(4) Condensation grafting of carbon black surface with rubber macromolecular end groups
The sulfhydryl group and the light base on the surface of the carbon black are converted into highly reactive functional groups by reacting with a highly active substance, and then reacted with a hydroxyl group-containing polymer such as polyester to form a graft polymer chain on the surface of the carbon black to strengthen the direct The firmness of the connection.
(5) Grafting of free radicals on the surface of carbon black
The aromatic fused ring and the quinoid structure on the surface of the carbon black have a trapping function on the free radicals, and can generate a radical-bearing polymer substance, which easily reacts with the surface of the carbon black to form a graft with the surface of the carbon black. A typical example is the modification of carbon black with long-chain unsaturated fatty acids in the presence of dicumyl peroxide (DCP) to achieve a flexible bond between the rubber and the carbon black to make the rubber gasket The flexing resistance and fatigue resistance are greatly improved.
(6) Surface modification of carbon black
Carbon black undergoes surface oxidation treatment, and the type and amount of surface functional groups change. The activity and polarity of the surface are improved, thereby reducing the tendency of agglomeration and greatly improving its dispersibility in the rubber matrix.
(7) Halogenation modification of carbon black surface
The functional groups on the surface of the carbon black can all produce a halogenation reaction. If a more electronegative chlorine atom is introduced into the surface of the carbon black, the type and amount of these functional groups can be changed, and the surface activity of the carbon black can be increased, thereby greatly increasing the dispersion of the modified carbon black in the rubber matrix. .
In summary, the surface functional group of carbon black determines the surface activity of carbon black, which satisfies the high performance and practical value of the rubber gasket.